CY7C4281 CY7C4291 64K/128K x 9 Deep Sync FIFOs Features Functional Description • High-speed, low-power, first-in first-out (FIFO) memories • 64K × 9 (CY7C4281) • 128K × 9 (CY7C4291) • 0.5-micron CMOS for optimum speed/power • High-speed 100-MHz operation (10-ns read/write cycle times) • Low power — ICC= 40 mA • • • • • • • • • Logic Block Diagram When WEN1 is LOW and WEN2/LD is HIGH, data is written into the FIFO on the rising edge of the WCLK signal. While WEN1, WEN2/LD is held active, data is continually written into the FIFO on each WCLK cycle. The output port is controlled in a similar manner by a free-running read clock (RCLK) and two read enable pins (REN1, REN2). In addition, the CY7C4281/91 has an output enable pin (OE). The read (RCLK) and write (WCLK) clocks may be tied together for single-clock operation or the two clocks may be run independently for asynchronous read/write applications. Clock frequencies up to 100 MHz are achievable. Depth expansion is possible using one enable input for system control, while the other enable is controlled by expansion logic to direct the flow of data. D0 − 8 Pin Configuration PLCC Top View WCLK WEN1 WEN2/LD D1 D0 PAF PAE GND FLAG PROGRAM REGISTER WRITE CONTROL REN1 RCLK REN2 OE EF RS PAE PAF FF 4 3 5 6 7 8 9 10 11 12 13 2 1 32 31 30 29 28 CY7C4281 CY7C4291 READ POINTER 27 26 25 24 23 22 21 14 15 16 17 18 19 20 EF FF Q0 Q1 Q2 WRITE POINTER FLAG LOGIC Dual Port RAMARRAY 64K x 9 128K x 9 D3 D2 INPUT REGISTER RS WEN1 WCLK WEN2/LD VCC Q8 Q7 Q6 Q5 Q3 Q4 • These FIFOs have nine-bit input and output ports that are controlled by separate clock and enable signals. The input port is controlled by a free-running clock (WCLK) and two write-enable pins (WEN1, WEN2/LD). D4 D5 D6 D7 D8 • — ISB = 2 mA Fully asynchronous and simultaneous read and write operation Empty, Full, and programmable Almost Empty and Almost Full status flags TTL compatible Output Enable (OE) pin Independent read and write enable pins Center power and ground pins for reduced noise Supports free-running 50% duty cycle clock inputs Width Expansion Capability 32-pin PLCC Pin-compatible density upgrade to CY7C42X1 family Pin-compatible density upgrade to IDT72201/11/21/31/41/51 The CY7C4281/91 are high-speed, low-power FIFO memories with clocked read and write interfaces. All are nine bits wide. The CY7C4281/91 are pin-compatible to the CY7C42X1 Synchronous FIFO family. Programmable features include Almost Full/Almost Empty flags. These FIFOs provide solutions for a wide variety of data buffering needs, including high-speed data acquisition, multiprocessor interfaces, and communications buffering. RESET LOGIC THREE-STATE OUTPUT REGISTER READ CONTROL OE Q0 – 8 Cypress Semiconductor Corporation Document #: 38-06007 Rev. *B RCLK REN1 REN2 • 3901 North First Street • San Jose, CA 95134 • 408-943-2600 Revised August 19, 2003 CY7C4281 CY7C4291 Pin Definitions Signal Name Description I/O Description D0 – 8 Data Inputs I Data Inputs for 9-bit bus. Q0 − 8 Data Outputs O Data Outputs for 9-bit bus. WEN1 Write Enable 1 I The only write enable when device is configured to have programmable flags. Data is written on a LOW-to-HIGH transition of WCLK when WEN1 is asserted and FF is HIGH. If the FIFO is configured to have two write enables, data is written on a LOW-to-HIGH transition of WCLK when WEN1 is LOW and WEN2/LD and FF are HIGH. WEN2/LD Dual Mode Pin Write Enable 2 I If HIGH at reset, this pin operates as a second write enable. If LOW at reset, this pin operates as a control to write or read the programmable flag offsets. WEN1 must be LOW and WEN2 must be HIGH to write data into the FIFO. Data will not be written into the FIFO if the FF is LOW. If the FIFO is configured to have programmable flags, WEN2/LD is held LOW to write or read the programmable flag offsets. Load REN1, REN2 Read Enable Inputs I Enables the device for Read operation. Both REN1 and REN2 must be asserted to allow a read operation. WCLK Write Clock I The rising edge clocks data into the FIFO when WEN1 is LOW and WEN2/LD is HIGH and the FIFO is not Full. When LD is asserted, WCLK writes data into the programmable flag-offset register. RCLK Read Clock I The rising edge clocks data out of the FIFO when REN1 and REN2 are LOW and the FIFO is not Empty. When WEN2/LD is LOW, RCLK reads data out of the programmable flag-offset register. EF Empty Flag O When EF is LOW, the FIFO is empty. EF is synchronized to RCLK. FF Full Flag O When FF is LOW, the FIFO is full. FF is synchronized to WCLK. PAE Programmable Almost Empty O When PAE is LOW, the FIFO is almost empty based on the almost empty offset value programmed into the FIFO. PAE is synchronized to RCLK. PAF Programmable Almost Full O When PAF is LOW, the FIFO is almost full based on the almost full offset value programmed into the FIFO. PAF is synchronized to WCLK. RS Reset I Resets device to empty condition. A reset is required before an initial read or write operation after power-up. OE Output Enable I When OE is LOW, the FIFO’s data outputs drive the bus to which they are connected. If OE is HIGH, the FIFO’s outputs are in High Z (high-impedance) state. CY7C4281 CY7C4291 Density 64k x 9 128k x 9 Package 32-pin PLCC 32-pin PLCC Selection Guide Maximum Frequency 7C4281/91-10 7C4281/91-15 7C4281/91-25 Unit 100 66.7 40 MHz Maximum Access Time 8 10 15 ns Minimum Cycle Time 10 15 25 ns Minimum Data or Enable Set-up Minimum Data or Enable Hold Maximum Flag Delay Active Power Supply Current (ICC1) Document #: 38-06007 Rev. *B 3 4 6 ns 0.5 1 1 ns 8 10 15 ns Commercial 40 40 40 mA Industrial 45 Page 2 of 16 CY7C4281 CY7C4291 Functional Description (continued) The CY7C4281/91 provides four status pins: Empty, Full, Programmable Almost Empty, and Programmable Almost Full. The Almost Empty/Almost Full flags are programmable to single-word granularity. The programmable flags default to Empty+7 and Full-7. The flags are synchronous, i.e., they change state relative to either the read clock (RCLK) or the write clock (WCLK). When entering or exiting the Empty and Almost Empty states, the flags are updated exclusively by the RCLK. The flags denoting Almost Full and Full states are updated exclusively by WCLK. The synchronous flag architecture guarantees that the flags maintain their status for at least one cycle. All configurations are fabricated using an advanced 0.5µ CMOS technology. Input ESD protection is greater than 2001V, and latch-up is prevented by the use of guard rings. Architecture The CY7C4281/91 consists of an array of 64K to 128K words of nine bits each (implemented by a dual-port array of SRAM cells), a read pointer, a write pointer, control signals (RCLK, WCLK, REN1, REN2, WEN1, WEN2, RS), and flags (EF, PAE, PAF, FF). Resetting the FIFO Upon power-up, the FIFO must be reset with a Reset (RS) cycle. This causes the FIFO to enter the Empty condition signified by EF being LOW. All data outputs (Q0–8) go LOW tRSF after the rising edge of RS. In order for the FIFO to reset to its default state, the user must not read or write while RS is LOW. All flags are guaranteed to be valid tRSF after RS is taken LOW. FIFO Operation When the WEN1 signal is active LOW, WEN2 is active HIGH, and FF is active HIGH, data present on the D0–8 pins is written into the FIFO on each rising edge of the WCLK signal. Similarly, when the REN1 and REN2 signals are active LOW and EF is active HIGH, data in the FIFO memory will be presented on the Q0–8 outputs. New data will be presented on each rising edge of RCLK while REN1 and REN2 are active. REN1 and REN2 must set up tENS before RCLK for it to be a valid read function. WEN1 and WEN2 must occur tENS before WCLK for it to be a valid write function. An output enable (OE) pin is provided to three-state the Q0–8 outputs when OE is asserted. When OE is enabled (LOW), data in the output register will be available to the Q0–8 outputs after tOE. If devices are cascaded, the OE function will only output data on the FIFO that is read enabled. The FIFO contains overflow circuitry to disallow additional writes when the FIFO is full, and underflow circuitry to disallow additional reads when the FIFO is empty. An empty FIFO maintains the data of the last valid read on its Q0–8 outputs even after additional reads occur. Write Enable 1 (WEN1) — If the FIFO is configured for programmable flags, Write Enable 1 (WEN1) is the only write enable control pin. In this configuration, when Write Enable 1 (WEN1) is LOW, data can be loaded into the input register and RAM array on the LOW-to-HIGH transition of every write clock (WCLK). Data is stored is the RAM array sequentially and independently of any on-going read operation. Write Enable 2/Load (WEN2/LD) — This is a dual-purpose pin. The FIFO is configured at Reset to have programmable flags or to have two write enables, which allows for depth expansion. If Write Enable 2/Load (WEN2/LD) is set active HIGH at Reset (RS = LOW), this pin operates as a second write enable pin. If the FIFO is configured to have two write enables, when Write Enable (WEN1) is LOW and Write Enable 2/Load (WEN2/LD) is HIGH, data can be loaded into the input register and RAM array on the LOW-to-HIGH transition of every write clock (WCLK). Data is stored in the RAM array sequentially and independently of any on-going read operation. Programming When WEN2/LD is held LOW during Reset, this pin is the load (LD) enable for flag offset programming. In this configuration, WEN2/LD can be used to access the four nine-bit offset registers contained in the CY7C4281/4291 for writing or reading data to these registers. When the device is configured for programmable flags and both WEN2/LD and WEN1 are LOW, the first LOW-to-HIGH transition of WCLK writes data from the data inputs to the empty offset least significant bit (LSB) register. The second, third, and fourth LOW-to-HIGH transitions of WCLK store data in the empty offset most significant bit (MSB) register, full offset LSB register, and full offset MSB register, respectively, when WEN2/LD and WEN1 are LOW. The fifth LOW-to-HIGH transition of WCLK while WEN2/LD and WEN1 are LOW writes data to the empty LSB register again. Figure 1 shows the registers sizes and default values for the various device types. 128K× 9 64K × 9 8 0 7 8 Empty Offset (LSB) Reg. Default Value = 007h Empty Offset (LSB) Reg. Default Value = 007h 0 8 7 0 8 (MSB) Default Value = 000h (MSB) Default Value = 000h 0 8 7 8 Full Offset (LSB) Reg Default Value = 007h (MSB) Default Value = 000h 0 7 Full Offset (LSB) Reg Default Value = 007h 0 8 7 0 7 0 8 (MSB) Default Value = 000h Figure 1. Offset Register Location and Default Values Document #: 38-06007 Rev. *B Page 3 of 16 CY7C4281 CY7C4291 It is not necessary to write to all the offset registers at one time. A subset of the offset registers can be written; then by bringing the WEN2/LD input HIGH, the FIFO is returned to normal read and write operation. The next time WEN2/LD is brought LOW, a write operation stores data in the next offset register in sequence. The contents of the offset registers can be read to the data outputs when WEN2/LD is LOW and both REN1 and REN2 are LOW. LOW-to-HIGH transitions of RCLK read register contents to the data outputs. Writes and reads should not be performed simultaneously on the offset registers. Programmable Flag (PAE, PAF) Operation Whether the flag offset registers are programmed as described in Table 1 or the default values are used, the programmable almost-empty flag (PAE) and programmable almost-full flag (PAF) states are determined by their corresponding offset registers and the difference between the read and write pointers. Table 1. Writing the Offset Registers LD WEN 0 0 Selection WCLK[1] Empty Offset (LSB) Empty Offset (MSB) Full Offset (LSB) Full Offset (MSB) 0 1 No Operation 1 0 Write Into FIFO 1 1 No Operation is greater than or equal to CY7C4281 (64K-m) and CY7C4291 (128K-m). PAF is set HIGH by the LOW-to-HIGH transition of WCLK when the number of available memory locations is greater than m. Table 2. Status Flags Number of Words in FIFO CY7C4281 0 CY7C4291 0 [2] [2] FF PAF PAE EF H H L L H H L H (n+1) to (65536 −(m+1)) (n+1) to (131072−(m+1)) H H H H (65536 − m)[3] to 65535 131072 − m)[3] to 131071 H L H H 65536 131072 L L H H 1 to n 1 to n Width Expansion Configuration Word width may be increased simply by connecting the corresponding input controls signals of multiple devices. A composite flag should be created for each of the end-point status flags (EF and FF). The partial status flags (PAE and PAF) can be detected from any one device. Figure 2 demonstrates a 18-bit word width by using two CY7C42X1s. Any word width can be attained by adding additional CY7C42X1s. When the CY7C42X1 is in a Width Expansion Configuration, the Read Enable (REN2) control input can be grounded (see Figure 2). In this configuration, the Write Enable 2/Load (WEN2/LD) pin is set to LOW at Reset so that the pin operates as a control to load and read the programmable flag offsets. Flag Operation The CY7C4281/91 devices provide five flag pins to indicate the condition of the FIFO contents. Empty, Full, PAE, and PAF are synchronous. Full Flag The number formed by the empty offset least significant bit register and empty offset most significant bit register is referred to as n and determines the operation of PAE. PAF is synchronized to the LOW-to-HIGH transition of RCLK by one flip-flop and is LOW when the FIFO contains n or fewer unread words. PAE is set HIGH by the LOW-to-HIGH transition of RCLK when the FIFO contains (n + 1) or greater unread words. The number formed by the full offset least significant bit register and full offset most significant bit register is referred to as m and determines the operation of PAF. PAE is synchronized to the LOW-to-HIGH transition of WCLK by one flip-flop and is set LOW when the number of unread words in the FIFO The Full Flag (FF) will go LOW when the device is full. Write operations are inhibited whenever FF is LOW regardless of the state of WEN1 and WEN2/LD. FF is synchronized to WCLK, i.e., it is exclusively updated by each rising edge of WCLK. Empty Flag The Empty Flag (EF) will go LOW when the device is empty. Read operations are inhibited whenever EF is LOW, regardless of the state of REN1 and REN2. EF is synchronized to RCLK, i.e., it is exclusively updated by each rising edge of RCLK. Note: 1. The same selection sequence applies to reading from the registers. REN1 and REN2 are enabled and a read is performed on the LOW-to-HIGH transition of RCLK. Document #: 38-06007 Rev. *B Page 4 of 16 CY7C4281 CY7C4291 RESET (RS) DATA IN (D) 18 RESET (RS) 9 9 READ CLOCK (RCLK) WRITECLOCK (WCLK) READ ENABLE 1 (REN1) WRITE ENABLE 1(WEN1) OUTPUT ENABLE (OE) WRITE ENABLE 2/LOAD (WEN2/LD) CY7C4281/91 CY7C4281/91 PROGRAMMABLE(PAF) PROGRAMMABLE(PAE) EMPTY FLAG (EF) #1 EMPTY FLAG (EF) #2 FULL FLAG (FF) # 1 FF FF EF EF 9 FULL FLAG (FF) # 2 DATA OUT (Q) 18 9 Read Enable 2 (REN2) Read Enable 2 (REN2) Figure 2. Block Diagram of 64k x 9/128k x 9 Deep Sync FIFO Memory Used in a Width Expansion Configuration Notes: 2. n = Empty Offset (n = 7 default value). 3. m = Full Offset (m = 7 default value). Document #: 38-06007 Rev. *B Page 5 of 16 CY7C4281 CY7C4291 DC Input Voltage ....................................... −0.5V to VCC + 0.5V Maximum Ratings (Above which the useful life may be impaired. For user guidelines, not tested.) Storage Temperature ....................................... −65°C to +150°C Ambient Temperature with Power Applied.................................................... −55°C to +125°C Output Current into Outputs (LOW)............................. 20 mA Static Discharge Voltage........................................... > 2001V (per MIL-STD-883, Method 3015) Latch-up Current..................................................... > 200 mA Operating Range[4] Supply Voltage to Ground Potential .................−0.5V to +7.0V Range DC Voltage Applied to Outputs in High-Z State ............................................−0.5V to VCC + 0.5V Ambient Temperature VCC Commercial 0°C to +70°C 5V ± 10% Industrial[5] −40°C to +85°C 5V ± 10% Electrical Characteristics Over the Operating Range Parameter Description Test Conditions VOH Output HIGH Voltage VCC = Min., IOH = −2.0 mA VCC = Min., IOL = 8.0 mA 7C42X1−15 7C42X1−25 Min. Min. Min. VOL Output LOW Voltage Input HIGH Voltage VIL Input LOW Voltage IIX Input Leakage Current VCC = Max. IOZL IOZH Output OFF, High Z Current OE > VIH, VSS < VO< VCC ICC1[6] Active Power Supply Current Max. 2.4 0.4 2.0 Average Standby Current Max. 2.4 VIH ISB[7] 7C42X1−10 Max. 2.4 V 0.4 VCC 2.0 −0.5 0.8 −10 +10 −10 +10 Unit 0.4 V VCC V VCC 2.0 −0.5 0.8 −0.5 0.8 V −10 +10 −10 +10 µA −10 +10 −10 +10 µA Com’l 40 40 40 mA Ind 45 45 45 mA Com’l 2 2 2 Ind 2 mA mA Capacitance[8] Parameter Description CIN Input Capacitance COUT Output Capacitance Test Conditions TA = 25°C, f = 1 MHz, VCC = 5.0V Max. Unit 5 pF 7 pF AC Test Loads and Waveforms[9, 10] R11.1KΩ ALL INPUT PULSES 5V OUTPUT 3.0V CL INCLUDING JIG AND SCOPE Equivalent to: THÉVENIN EQUIVALENT 420Ω OUTPUT R2 680Ω 90% 10% GND ≤ 3 ns 90% 10% ≤ 3 ns 1.91V Note: 4. The voltage on any input or I/O pin cannot exceed the power pin during power-up. 5. TA is the “instant on” case temperature. 6. Input signals switch from 0V to 3V with a rise/fall time of less than 3 ns, clocks and clock enables switch at maximum frequency 20 MHz, while data inputs switch at 10 MHz. Outputs are unloaded. Icc1(typical) = (20 mA + (freq – 20 MHz)*(0.7 mA/MHz)). 7. All inputs = VCC – 0.2V, except WCLK and RCLK (which are at frequency = 0 MHz). All outputs are unloaded. 8. Tested initially and after any design or process changes that may affect these parameters. 9. CL = 30 pF for all AC parameters except for tOHZ. 10. CL = 5 pF for tOHZ. Document #: 38-06007 Rev. *B Page 6 of 16 CY7C4281 CY7C4291 Switching Characteristics Over the Operating Range Parameter Description 7C42X1-10 7C42X1-15 7C42X1-25 Min. Min. Min. Max. 100 Max. Unit 40 MHz 15 ns Clock Cycle Frequency tA Data Access Time 2 tCLK Clock Cycle Time 10 15 25 ns tCLKH Clock HIGH Time 4.5 6 10 ns tCLKL Clock LOW Time 4.5 6 10 ns tDS Data Set-up Time tDH Data Hold Time tENS Enable Set-up Time tENH Enable Hold Time Width[11] 8 66.7 Max. tS 2 10 2 3 4 6 ns 0.5 1 1 ns 3 4 6 ns 0.5 1 1 ns tRS Reset Pulse 10 15 25 ns tRSS Reset Set-up Time 8 10 15 ns tRSR Reset Recovery Time 8 tRSF Reset to Flag and Output Time tOLZ Output Enable to Output in Low tOE Output Enable to Output Valid 10 10 Z[12] Z[12] 0 15 15 0 3 7 3 3 7 3 ns 25 0 ns ns 8 3 12 ns 8 3 tOHZ Output Enable to Output in High 12 ns tWFF Write Clock to Full Flag 8 10 15 ns tREF Read Clock to Empty Flag 8 10 15 ns tPAF Clock to Programmable Almost-Full Flag 8 10 15 ns tPAE Clock to Programmable Almost-Full Flag 15 ns tSKEW1 Skew Time between Read Clock and Write Clock for Empty Flag and Full Flag 5 6 10 ns tSKEW2 Skew Time between Read Clock and Write Clock for Almost-Empty Flag and Almost-Full Flag 10 15 18 ns 8 10 Notes: 11. Pulse widths less than minimum values are not allowed. 12. Values guaranteed by design, not currently tested. Document #: 38-06007 Rev. *B Page 7 of 16 CY7C4281 CY7C4291 Switching Waveforms Write Cycle Timing tCLK tCLKH tCLKL WCLK tDS tDH D0 –D17 tENS tENH WEN1 NO OPERATION NO OPERATION WEN2 (if applicable) tWFF tWFF FF tSKEW1 [13] RCLK REN1, REN2 Read Cycle Timing tCKL tCLKH tCLKL RCLK tENS tENH REN1, REN2 NO OPERATION tREF tREF EF tA VALID DATA Q0 –Q17 tOLZ tOHZ tOE OE tSKEW1[14] WCLK WEN1 WEN2 Notes: 13. tSKEW1 is the minimum time between a rising RCLK edge and a rising WCLK edge to guarantee that FF will go HIGH during the current clock cycle. If the time between the rising edge of RCLK and the rising edge of WCLK is less than tSKEW1, then FF may not change state until the next WCLK rising edge. 14. tSKEW1 is the minimum time between a rising WCLK edge and a rising RCLK edge to guarantee that EF will go HIGH during the current clock cycle. It the time between the rising edge of WCLK and the rising edge of RCLK is less than tSKEW2, then EF may not change state until the next RCLK rising edge. Document #: 38-06007 Rev. *B Page 8 of 16 CY7C4281 CY7C4291 Switching Waveforms (continued) Reset Timing [15] tRS RS tRSS tRSR tRSS tRSR tRSS tRSR REN1, REN2 WEN1 WEN2/LD [17] tRSF EF,PAE tRSF FF,PAF tRSF Q0 - Q8 OE=1 [16] OE=0 Notes: 15. The clocks (RCLK, WCLK) can be free-running during reset. 16. After reset, the outputs will be LOW if OE = 0 and three-state if OE=1. 17. Holding WEN2/LD HIGH during reset will make the pin act as a second enable pin. Holding WEN2/LD LOW during reset will make the pin act as a load enable for the programmable flag offset registers. Document #: 38-06007 Rev. *B Page 9 of 16 CY7C4281 CY7C4291 Switching Waveforms (continued) First Data Word Latency after Reset with Read and Write WCLK tDS D0 –D8 D0 D1 (FIRST VALID WRITE) D2 D3 D4 tENS tFRL [18] WEN1 WEN2 (if applicable) tSKEW1 RCLK tREF EF tA tA [19] REN1, REN2 Q0 –Q8 D0 D1 tOLZ tOE OE Notes: 18. When tSKEW1 > minimum specification, tFRL (maximum) = tCLK + tSKEW2. When tSKEW1 < minimum specification, tFRL (maximum) = either 2*tCLK + tSKEW1 or tCLK + tSKEW1. The Latency Timing applies only at the Empty Boundary (EF = LOW). 19. The first word is available the cycle after EF goes HIGH, always. Document #: 38-06007 Rev. *B Page 10 of 16 CY7C4281 CY7C4291 Switching Waveforms (continued) Empty Flag Timing WCLK tDS tDS DATA WRITE 2 DATA WRITE 1 D0 –D8 tENH WEN1 tENH tENS tENS tENS tENH tENS tENH WEN2 (if applicable) tFRL [18] tFRL [18] RCLK tSKEW1 tREF tREF tREF tSKEW2 EF REN1, REN2 LOW OE tA Q0 –Q8 DATA IN OUTPUT REGISTER Document #: 38-06007 Rev. *B DATA READ Page 11 of 16 CY7C4281 CY7C4291 Switching Waveforms (continued) Full Flag Timing NO WRITE NO WRITE WCLK tSKEW1[13] [13] tDS DATA WRITE tSKEW1 DATA WRITE D0 –D8 tWFF tWFF tWFF FF WEN1 WEN2 (if applicable) RCLK tENH REN1, REN2 OE tENH tENS tENS LOW tA Q0 –Q8 tA DATA READ DATA IN OUTPUT REGISTER NEXT DATA READ Programmable Almost Empty Flag Timing tCLKL tCLKH WCLK tENS tENH WEN1 WEN2 (if applicable) tENS tENH Note 21 PAE N + 1 WORDS IN FIFO tSKEW2 [20] tPAE Note 22 tPAE RCLK tENS tENS tENH REN1, REN2 Notes: 20. tSKEW2 is the minimum time between a rising WCLK and a rising RCLK edge for PAE to change state during that clock cycle. If the time between the edge of WCLK and the rising RCLK is less than tSKEW2, then PAE may not change state until the next RCLK. 21. PAE offset = n. 22. If a read is preformed on this rising edge of the read clock, there will be Empty + (n−1) words in the FIFO when PAE goes LOW. Document #: 38-06007 Rev. *B Page 12 of 16 CY7C4281 CY7C4291 Switching Waveforms (continued) Programmable Almost Full Flag Timing tCLKL tCLKH [23] WCLK tENS tENH WEN1 WEN2 (if applicable) Note 24 tPAF tENS tENH PAF (FULL −M) WORDS IN FIFO [25] FULL − (M+1)WORDS IN FIFO tSKEW2 [26] tPAF RCLK tENS tENS tENH REN1, REN2 Write Programmable Registers tCLK tCLKL tCLKH WCLK tENS tENH WEN2/LD tENS WEN1 tDS tDH D0 –D8 PAE OFFSET LSB PAE OFFSET MSB PAF OFFSET LSB PAF OFFSET MSB Notes: 23. If a write is performed on this rising edge of the write clock, there will be Full − (m−1) words of the FIFO when PAF goes LOW. 24. PAF offset = m. 25. 16,384 − m words for CY7C4281, 32,768 − m words for CY4291. 26. tSKEW2 is the minimum time between a rising RCLK edge and a rising WCLK edge for PAF to change during that clock cycle. If the time between the rising edge of RCLK and the rising edge of WCLK is less than tSKEW2, then PAF may not change state until the next WCLK. Document #: 38-06007 Rev. *B Page 13 of 16 CY7C4281 CY7C4291 Switching Waveforms (continued) Read Programmable Registers tCLK tCLKL tCLKH RCLK tENS tENH WEN2/LD tENS PAF OFFSET MSB REN1, REN2 tA UNKNOWN Q0 –Q15 PAE OFFSET LSB PAE OFFSET MSB PAF OFFSET LSB Ordering Information 64K x 9 Deep Sync FIFO Speed (ns) 10 Ordering Code Package Name Package Type Operating Range CY7C4281-10JC J65 32-Lead Plastic Leaded Chip Carrier Commercial CY7C4281-10JI J65 32-Lead Plastic Leaded Chip Carrier Industrial 15 CY7C4281-15JC J65 32-Lead Plastic Leaded Chip Carrier Commercial 25 CY7C4281-25JC J65 32-Lead Plastic Leaded Chip Carrier Commercial 128K x 9 Deep Sync FIFO Speed (ns) 10 Ordering Code Package Name Package Type Operating Range CY7C4291-10JC J65 32-Lead Plastic Leaded Chip Carrier Commercial CY7C4291-10JI J65 32-Lead Plastic Leaded Chip Carrier Industrial 15 CY7C4291-15JC J65 32-Lead Plastic Leaded Chip Carrier Commercial 25 CY7C4291-25JC J65 32-Lead Plastic Leaded Chip Carrier Commercial Document #: 38-06007 Rev. *B Page 14 of 16 CY7C4281 CY7C4291 Package Diagrams 32-Lead Plastic Leaded Chip Carrier J65 51-85002-*B All product and company names mentioned in this document are the trademarks of their respective holders. Document #: 38-06007 Rev. *B Page 15 of 16 © Cypress Semiconductor Corporation, 2003. The information contained herein is subject to change without notice. Cypress Semiconductor Corporation assumes no responsibility for the use of any circuitry other than circuitry embodied in a Cypress Semiconductor product. Nor does it convey or imply any license under patent or other rights. Cypress Semiconductor does not authorize its products for use as critical components in life-support systems where a malfunction or failure may reasonably be expected to result in significant injury to the user. The inclusion of Cypress Semiconductor products in life-support systems application implies that the manufacturer assumes all risk of such use and in doing so indemnifies Cypress Semiconductor against all charges. CY7C4281 CY7C4291 Document History Page Document Title: CY7C4281, CY7C4291 64K/128K X 9 Deep Sync FIFOs Document Number: 38-06007 REV. ECN NO. Issue Date Orig. of Change Description of Change ** 106468 07/12/01 SZV Change from Spec number: 38-00587 to 38-06007 *A 122259 12/26/02 RBI Power up requirements added to Operating Range Information *B 127854 08/22/03 FSG Removed Preliminary Fixed empty flag timing diagram Switching waveform diagram typo fixed Document #: 38-06007 Rev. *B Page 16 of 16